Change mmc_blk_issue_rw_rq() to become asynchronous.The execution flow looks like this:The mmc-queue calls issue_rw_rq(), which sends the requestto the host and returns back to the mmc-queue. The mmc-queue callsissue_rw_rq() again with a new request. This new request is prepared,in isuue_rw_rq(), then it waits for the active request to complete beforepushing it to the host. When to mmc-queue is empty it will callisuue_rw_rq() with req=NULL to finish off the active requestwithout starting a new request.